Snowball Earth

Evidence of glaciation in tropical regions appears to have spawned the idea of Snowball Earth. This is dated to the remote geological past, the Neoproterozoic and the Paleoproterozoic. The glaciations are reputed to have lasted for millions of years and to have embraced every region of the globe. Unfortunately, earth scientists seem to have failed to come up with a logical explanation as to how Snowball Earth became our kind of Earth – with ice restricted to the Poles, or at high altitudes. One study claimed it would have required the atmosphere to consist of 20 per cent co2. This was refuted as paleogeochemical tests appear to show thee was a lot less than 10 per cent – perhaps only 1 per cent. A new paper in Geophysical Research Letters blames it all on clouds – the cooling and the warming. That is like having your cake and eating the whole slab in one go. Needless to say co2 has a role and it is not just those dratted clouds messing things upsadaisy – see http://phys.org/print272050597.html .. and the throwaway sentence, we may note,  '… some scientists suspect that Snowball Earth never happened'.